Dr. Bradley's research is focused on understanding the mechanisms for cardiovascular disease in patients with sleep apnea. Understanding the mechanisms for cardiovascular disease in this population is important to appropriately manage and treat sleep apnea and co-existing cardiovascular disease in the clinical setting. For example, people with untreated sleep apnea are at a three fold higher risk for hypertension. Further, when hypertension is present it is often resistant to drug therapy until sleep disordered breathing is eliminated. Effectively treating sleep apnea can decrease blood pressure significantly.

Obstructive sleep apnea affects 15 million Americans and occurs in up to 5% of men and 3% of women. The common characteristics of obstructive sleep apnea include obesity, male gender, large neck circumference, daytime tiredness, fatigue, and snoring. One of the hallmark signs of sleep apnea is witnessed cessation of breathing during sleep. Although obstructive sleep apnea occurs in children and adolescents, it is more common in middle-aged adults with prevalence increasing with age. A diagnostic sleep study (polysomnography) determines the severity or number of episodes of apnea and hypopnea during sleep. The main treatment to alleviate obstructive sleep apnea is continuous positive airway pressure therapy. This type of therapy is delivered by a bedside machine that provides room air through a small mask secured over the nose during the night.

There are well established pathophysiologic factors, such as obesity, that explain the development and progression of cardiovascular disease. Other known factors include activation of the central sympathetic nervous system, increases in circulating catecholamine levels, impaired cardiovascular variability, and activation of the endothelin system. These well known mechanisms for cardiovascular disease also occur in relatively healthy people that just have obstructive sleep apnea. Patients with severe sleep apnea who are free of cardiovascular disease have impaired endothelium dependent vasodilation. This type of vasculopathy is seen early in hypertension, diabetes, heart failure and in arteriosclerosis. The presence of obesity worsens sleep apnea. The corollary to this may also be true as patients with sleep apnea have increased leptin resistance and weight gain. It appears that many of the known factors for poor cardiovascular heath also occur in sleep apnea. Emerging evidence suggests that untreated sleep apnea may predispose to cardiovascular disease.